Fuel cells combine hydrogen and oxygen without combustion to form water and to produce direct current electric power. The process can be described as electrolysis in reverse. Fuel cells have been pursued as a source of power for transportation because of their high energy efficiency (unmatched by heat engine cycles), their potential for fuel flexibility, and their extremely low emissions. Fuel cells have potential for stationary and vehicular power applications; however, the commercial viability of fuel cells for power generation in stationary and transportation applications depends upon solving a number of manufacturing, cost, and durability problems.
The most promising fuel cells for widespread transportation use are PEM fuel cells. PEM fuel cells operate at low temperatures, produce fast transient response, and have relatively high energy density compared to other fuel cell technologies. Any fuel cell design must: (a) allow for supply of the reactants (typically hydrogen and oxygen); (b) allow for mass transport of product (water) and inert gases (nitrogen and carbon dioxide from air); and (c) provide electrodes to support catalyst, collect electrical charge, and dissipate heat. Electrical and thermal resistance, reactant pressures, temperatures, surface area, catalyst availability, and geometry are the main factors affecting the performance and efficiency of a fuel cell.
Problems encountered with PEM fuel cells are the need to reduce thermal and mechanical stress concentrations and to increase integrity and performance. Current phosphoric acid and PEM fuel cells rely on fiat-plate electrodes. Flat plate PEM fuel cells suffer from reactant flow distribution problems which can cause inefficient operation and even premature failure of the fuel cell.
Certain fuel cells--solid-oxide, ceramic, high-temperature fuel cells--have been described in tubular configurations. The use of tubular, or capillary PEM fuel cells could lead to lower thermal stress and reduced manufacturing costs. Unfortunately, solid-oxide cylindrical fuel cell construction, materials, and methods are not directly applicable to PEM fuel cells.
Simple methods are needed to manufacture cylindrical PEM fuel cells.